/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.skywalking.library.kubernetes;

import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import io.fabric8.kubernetes.api.model.Service;
import io.fabric8.kubernetes.client.KubernetesClientBuilder;
import lombok.SneakyThrows;
import org.slf4j.LoggerFactory;

import java.time.Duration;
import java.util.Collections;
import java.util.List;
import java.util.Optional;

public enum KubernetesServices {
    INSTANCE;

    private final LoadingCache<KubernetesServices, List<Service>> services;
    private final LoadingCache<ObjectID, Optional<Service>> serviceByID;

    @SneakyThrows
    KubernetesServices() {
        final CacheBuilder<Object, Object> cacheBuilder =
            CacheBuilder.newBuilder()
                        .expireAfterWrite(Duration.ofMinutes(3));

        services = cacheBuilder.build(CacheLoader.from(() -> {
            try (final var kubernetesClient = new KubernetesClientBuilder().build()) {
                return kubernetesClient
                        .services()
                        .inAnyNamespace()
                        .list()
                        .getItems();
            } catch (Exception e) {
                LoggerFactory.getLogger(getClass()).error("Failed to list Services.", e);
                return Collections.emptyList();
            }
        }));

        serviceByID = cacheBuilder.build(new CacheLoader<>() {
            @Override
            public Optional<Service> load(ObjectID id) {
                try (final var kubernetesClient = new KubernetesClientBuilder().build()) {
                    return Optional.ofNullable(
                        kubernetesClient
                            .services()
                            .inNamespace(id.namespace())
                            .withName(id.name())
                            .get());
                }
            }
        });
    }

    @SneakyThrows
    public List<Service> list() {
        return services.get(this);
    }

    @SneakyThrows
    public Optional<Service> findByID(final ObjectID id) {
        return serviceByID.get(id);
    }
}
